Handheld vision tester and calibration thereof

ABSTRACT

In one aspect, there is provided an embodiment of a calibration system for use with a vision tester having a display. In this particular embodiment, the calibration system comprises a calibration stand and a reflective surface. The calibration stand is configured to hold the vision tester. The reflective surface is coupled to the calibration stand and is oriented substantially parallel to the display. The calibration stand is configured to hold the display of the vision tester at a fixed distance from the reflective surface.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No. 13/319,317filed on Nov. 7, 2011, entitled “Handheld Vision Tester and CalibrationThereof”, which is the National Stage of, and therefore claims thebenefit of, International Application No. PCT/US2010/034086 filed on May7, 2010, entitled “Handheld Vision Tester and Calibration Thereof,”which was published in English under International Publication Number WO2010/132305 on Nov. 18, 2010, and has a priority date of May 9, 2009based on provisional application No. 61/176,885 filed by MichaelBartlett, et al. Both of the above applications are commonly assignedwith this National Stage application and are incorporated herein byreference in their entirety.

TECHNICAL FIELD OF THE INVENTION

This invention relates to techniques for the design and implementationof a vision testing system including calibration techniques.

BACKGROUND OF THE INVENTION

Vision testing is normally carried out today either through observationof vision testing charts or through professional evaluation includingimaging of the inside of the eye and other advanced diagnostic tools.Professional evaluation is effective in analyzing many vision disorders,but is expensive and may not be available in rural and remote areas.Observation of vision testing charts is effective, but is bulky andcumbersome as the charts are normally mounted on a wall and the testsubject must observe them from some distance. While limited, use ofvision testing charts and professional evaluations are effective formany common vision disorders such as focusing disorders. However, thereare some vision diseases, such as diabetic retinopathy, age-relatedmacular degeneration, and other vision diseases where ongoing monitoringof vision is critically important. Such diseases may become active atspecific times and, if not treated, could result in irrecoverable visionloss or even blindness.

Consequently, a small and low-cost device that allows patients sufferingfrom these diseases to conveniently monitor their vision is desirable.Techniques that help to ensure such a system operates properly so thatit provides dependable test results are highly desirable. And additionaltechniques such as vision aids that help a patient in their daily life;electronic magnifier functions; auxiliary imaging and display systems;techniques to ensure the patient taking a test is the properlyidentified and is actively engaged; and other techniques to ensureaccurate testing are also desirable.

SUMMARY OF THE INVENTION

To address the above-discussed deficiencies of the prior art, in oneembodiment, there is provided a calibration system for use with a visiontester having a display. In this particular embodiment, the calibrationsystem comprises a calibration stand and a reflective surface. Thecalibration stand is configured to hold the vision tester. Thereflective surface is coupled to the calibration stand and is orientedsubstantially parallel to the display. The calibration stand isconfigured to hold the display of the vision tester at a fixed distancefrom the reflective surface.

In another embodiment, there is provided a calibration system for usewith a vision tester having a display. The calibration system comprisesa reflective surface and a camera. The reflective surface is orientedand configured to reflect images displayed on the display of the visiontester. The camera is associated with the vision tester and isconfigured to allow the vision tester to employ the reflected images tocalibrate and verify functionality of the vision tester.

The foregoing has outlined various features of the invention so thatthose skilled in the pertinent art may better understand the detaileddescription of the invention that follows. Additional features of theinvention will be described hereinafter that form the subject of theclaims of the invention. Those skilled in the pertinent art shouldappreciate that they can readily use the disclosed conception andspecific embodiment as a basis for designing or modifying otherstructures for carrying out the same purposes of the invention. Thoseskilled in the pertinent art should also realize that such equivalentconstructions do not depart from the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the invention, reference is nowmade to the following descriptions taken in conjunction with theaccompanying drawings, in which:

FIG. 1 shows a handheld device suitable for running a vision test;

FIG. 2 a shows a handheld device mounted in a calibration stand;

FIG. 2 b shows a perspective view of a handheld device mounted in acalibration stand;

FIG. 2 c shows an image suitable for use for calibration; and

FIG. 3 shows a fundus imaging system

DETAILED DESCRIPTION

In FIG. 1, an electronic handheld device 100 is shown. The handhelddevice 100 may include a case 102, a display 104, a cursor control 110,a fingerprint sensor 114, a camera 112, a first button 106, a secondbutton 108, a power connector 116, and an interface port 118. Thedisplay 104 may include touch-screen capability so that the handhelddevice 100 can be controlled by touching the display 104 inpre-specified locations or manners within certain timeframes. Thefingerprint sensor 114 allows the handheld device 100 to identify theperson using it. The cursor control 110 is a button that may be pressedto move a cursor across the display 104 and position it in a desiredlocation. Pressing the cursor control 110 may also be used to triggeroperations and to control the handheld device 100. Alternativeimplementations of cursor controls include track balls, joysticks, touchpads, and other approaches may also be used in place of the cursorcontrol 110 as shown in FIG. 1. The first button 106 and the secondbutton 108 may be used to control the handheld device 100 and to operatefunctions of the handheld device 100. It is noted that the handhelddevice 100 may be operated through manipulation of the display 104 if atouch-screen capability is included, through the cursor control 110,through the fingerprint sensor 114, through the first button 106 andthrough the second button 108. Additional buttons and controls arepossible including buttons and controls on the sides and back of thehandheld device 100. It is also possible to include additional buttons,displays, and other forms of input devices.

The case 102 of the handheld device 100 may be constructed from metals,plastics, or other materials. While not shown in FIG. 1, the handhelddevice 100 may include removable panels on its front, back, or sides toallow batteries, memory cards, or optional accessories to be installed,connected, or removed. The power connector 116 allows the device to bepowered from an external electrical power source that may supply AC orDC power to the handheld device 100. The interface port 118 allows thehandheld device 100 to be connected to an external host computer,external cameras, external calibration or test equipment, externalaccessories, or other systems or devices the user may desire to connectit to. It is also possible that the interface port 118 or the powerconnector 116 could be configured to supply battery power from thehandheld device 100 to an external device or interface connected tothem. The interface port 118 may be constructed from multiple physicalinterfaces and protocols. Some examples are Universal Serial Bus (USB),P1394, Ethernet, RS232, and many other possible interfaces. In additionto the interface port 118, the handheld device 100 may include wirelessconnectivity. Bluetooth, IEEE802.11, Zigbee, and many other wirelesscommunications protocols and radio electronics may be included in thehandheld device 100. The wired and or wireless connectivity of thehandheld device 100 allows it to send information to a network service,host computer, or other computing device; and also allows forcalibration, configuration, test protocols, software updates, and otheruseful information to be sent from a host computer or other dataprocessing device or interface to the handheld device 100. The procedurefor allowing the handheld device 100 to either send data out over itswired or wireless interfaces or to receive information from othersources should normally include security features to ensure that theusers information and privacy are not compromised and also to ensurethat configuration, calibration, and other important factors of thehandheld device 100 operation cannot be compromised illicitly oraccidentally.

The camera 112 can be used to ensure that the same person is taking thetest throughout the test sequence and an image of the user can becompared to images from past tests to help ensure that the person takingthe test is indeed the correct person. The handheld device 100 canperform this operation by image analysis of an image or images providedfrom camera 112. Additionally, the camera 112 can be used to check thatthe user is awake, upright, and appears to be capable and activelyengaged in taking the vision test.

In addition to delivering vision tests to a user, the handheld device100 can also serve as a vision aid to the user. The camera 112 can beused as a still image camera or as a video camera and allow the user totake images and then enlarge them on the display 104 so that they areeasier to observe. In addition to enlarging the images, the handhelddevice 100 can also provide image or video processing capability tosharpen, detail, provide additional contrast, color tint, or otherwisealter the image or video sequence so that it is easier for the user toview it. Of course, additional cameras can be mounted on other parts ofthe handheld device 100 in addition or in place of the camera 112 shownin FIG. 1. For use as a vision aid, it may be beneficial, for example,to include a second camera on the handheld device 100 that pointsopposite the direction of the camera 112 shown (that is, this additionalcamera would point into the page in FIG. 1). Additionally, a camera canbe mounted behind the display 104 in place of or in addition to thecamera 112 shown in FIG. 1. The camera 112, as shown in the embodimentof FIG. 1, may be beneficial in generating an “enhanced mirror” since itfaces the user and can simply put the image it has generated on thedisplay 104 in an enlarged or enhanced view. Special cameras, such asnight vision cameras, may also be included in the handheld device 100.Of course, any other wavelength specific camera may be included in thehandheld device 100. In addition to displaying information, the handhelddevice 100 may also include image analysis capability to automaticallyrecognize persons, places, or things by analyzing images taken from thehandheld device's 100 camera (or cameras). It is also possible to addauxiliary displays to the handheld device 100 or to use the interface118 or wireless connectivity to move images and/or video to an externalvideo monitor. Auxiliary displays suitable for use with the handhelddevice 100 include LCD display panels, CRT displays, light processingdisplay devices, head mounted displays, binocular display devices,virtual reality viewers, and many other types of displays. One exampleis use of the very small projectors that are now available and can beincorporated into small devices and allow images and video to beexpanded for easy viewing. These small projectors are sometimes referredto as pico projectors. Such a pico projector may be physicallyintegrated into the handheld device 100 or may be used as an externalseparate device connected to the handheld device 100 through a wired orwireless communication link.

The functions of the handheld device 100 shown in FIG. 1 may also beincorporated into electronic handheld devices that are already used forother functions. That is, the function delivered by the handheld device100 may be implemented on a portable game console, a cellular phone, apersonal digital assistant, a netbook computer, a notebook computer, ablood glucose meter, or many other electronic devices. The ability tocombine many functions together into a single device allows forconvenience for the user and also allows for beneficial combinedfunctionality in some cases. For example, if the handheld device 100 ofFIG. 1 includes the function of a glucometer (also known as a bloodglucose meter), the user can record their blood glucose level when eachvision test is taken so that a more complete record of vision capabilityand blood glucose can be generated. Of course, other biomedicalmeasurements of a user could also be recorded, such as, but not limitedto, blood pressure, heart rate, pupil dilation, iris color changes,eyelash growth, enzyme levels, etc. If the handheld device includes apositioning technology such as the Global Positioning System (GPS), therecords of vision testing can be location stamped so that the user canmore easily remember where they took each test and what the testingconditions were. Of course, the handheld device 100 can easily includecalendar and clock functions so that test results may also be time anddate stamped.

In FIG. 2 a, a calibration stand 200 is shown with the handheld device100 mounted in it. The calibration stand 200 comprises a base 202 and amirror 204. The calibration stand 200 positions the handheld device 100at a fixed distance and orientation relative to the mirror 204 so that atest image 206 creates a reflection 208 that can be observed by thecamera 112 (the camera is not explicitly visible in FIG. 2 a, but it'srelative position is clear from FIG. 1, so it is identified consistentlyby the numbering in FIG. 2 a). Please note that the test image 206 andthe reflection 208 are shown just in front of the handheld device 100and the mirror 204 in the cross sectional view shown in FIG. 2 a. Ofcourse, they would in practice actually appear on the surface of thehandheld device's 100 display 104 and, respectively, on the surface ofthe mirror 204, but such a view is not possible in a cross sectionaldrawing. The handheld device 100 is inserted into the base 202 and aself-testing and calibration sequence is initiated by the user to ensurethat the handheld device 100 is operating properly and can provide goodquality measurements. The handheld device 100 can display a wide rangeof images and observe them back through it's camera to ensure that theshape, color, contrast, size, and other aspects of the images aredisplayed as they should be. The calibration stand 200 is clearlydesirable for such self-testing and self-calibration, but it is notedthat this could be undertaken by simply holding the device in front of areflective surface and initiating the self-testing and calibrationsequence. Of course, given the potential for different distances,movement of the handheld device, and other factors, the use of acalibration stand 200 may be preferred.

The base 202 may be fabricated from metals, wood, plastics, or othermaterials. It may include features such as accurately formed surfaces,keyed openings, mechanical guides, and other features to keep thehandheld device 100 accurately and consistently in place. The base 202may also include fabrics, cushions, gaskets, felt linings, or otherfeatures to protect the handheld device 100 from being scratched ordamaged when it is inserted and removed from the base 202. And the base202 may also include mechanical features that secure the handheld device100 such as straps, clamps, snaps, buckles, or other features. Themirror 204 may be a glass mirror or may be made from polished metals,metal film laminated on plastics or other materials, or may beconstructed in other ways to provide a substantially reflective surface.Normally, the mirror 204 would be constructed to be highly reflective ofvisible light, but in the case that it has limited reflectivity orinconsistent reflectivity for some wavelengths of light, the handhelddevice 100 may compensate for this limitation through adjustment factorsincluded in its calibration routine. Similarly, if the camera 112provides higher sensitivity to some wavelengths of light, the handhelddevice 100 may compensate for it with information about the cameras 112sensitivity as a function of wavelength.

In another embodiment, the base 202 of calibration stand 200 couldinclude an auxiliary camera in place of mirror 204. In this embodiment,the auxiliary camera would be oriented toward the display of handhelddevice 100 such that test image 206 is captured by the auxiliary camera.The auxiliary camera could interface with handheld device 100 forcalibration purposes or could interface with an external device toanalyze calibration of the handheld tester.

The handheld device 100 may keep track of calendar dates and times andrequire that it be operated through its self-testing and calibrationsequence on a regular basis. The user may be reminded electronically ofthe need for this with visible, audible, or other signals or messages.The handheld device 100 may refuse to operate and collect user testresults if it has not been acceptably self-tested and calibrated withina sufficient time interval. Further, if the handheld device 100 detectsthat it has possibly been modified, the case 102 has been opened, highlevels of mechanical shock or acceleration have been measured, or otherfactors are present that bring the proper condition of the device intoquestion; the handheld device 100 may demand that the user run theself-testing and calibration sequence with acceptable results beforefurther testing takes place.

FIG. 2 b shows a perspective view of a handheld device 100 mounted in acalibration stand 200 including a base 202 and mirror 204. This view isshown to avoid any confusion related to the similar view of a handhelddevice 100 in a calibration stand 200 shown in FIG. 2 a. On the mirror204, a reflection 220 of the handheld device 100 is visible. Thisreflection 220 may be analyzed as already described with regard to FIG.2 a by using the camera 112 to create an image of the reflection 220 anduse of data processing functions in the handheld device 100 to analyzethe calibration image 222 visible in the reflection 220. Note that thecamera 112 is not actually visible in FIG. 2 b, but the camerareflection 224 of camera 112 is visible. The generation of a calibrationimage 222 will be discussed next with regard to FIG. 2 c.

FIG. 2 c shows a calibration image 240 that may be used for calibrationand testing of the handheld device 100 either through use of thecalibration stand 200 or with a reflective surface as described above.In the course of testing and calibrating the handheld device 100, acalibration image 240 is displayed on the display 104 and the reflectionof the calibration image 240 is observed with a camera 112. A very widevariety of calibration images 240 may be used. The calibration image 240shown in FIG. 2 c includes crosses 244, circles 246, squares 248, andtriangles 250 inside display boundary 242. The shapes shown in thecalibration image 240 are shown in black and white for convenience.However, a very wide variety of shapes, images, features, shadings,textures, colors, line weights, and other aspects may be used in animage for calibration and handheld device 100 testing purposes. Forexample, rectangles, wavy lines, ellipses, trapezoids, and very manyother shapes and images displayed in all possible colors, shadings,brightness levels, and other factors may be used as test images or aspart of a test image. And, in addition to stationary images, movingimages and video images may be used. Many standard video and imagecalibration charts may also be used.

FIG. 3 shows a fundus imaging system 300. A cross section of an eyeball302 and a schematic of how illumination might be applied so that fundusphotos of the retina 304 may be taken are shown. Fundus photography iswidely used to take images of the retina 304 of the eyeball 302. Fundusphotos are taken by using special lighting systems to illuminate theinside of the eye and to then take a photograph of the retina 304through the pupil of the eyeball 302. In FIG. 3, light emitting diodes310 are shown to illuminate the inside of the eye. Other lightingtechniques are possible such as scanning lasers, incandescent bulbs, andother techniques. Light emitting diodes 310 are presently preferred fortheir small size, low cost, and high efficiency. While only two lightemitting diodes 310 are shown in FIG. 3, the actual embodiment mightinclude a full circle of light emitting diodes 310 around the lens 318and imager 312. Many possible forms of the camera 112 of the handhelddevice 100 are possible, but most are based on a simple lens 318 andimager 312. Many types of imagers such as CMOS image sensors, CCD(Charge Coupled Device) imagers, and other imagers may be used. Also,the lens 318 may be a fixed lens or a variable focal length lens and maybe formed from glass, plastic, or other possible materials. It is notedthat the camera function made up of the lens 318 and imager 312 may bethose of the camera 112 shown in FIG. 1 or may be a separate cameramounted in the handheld device 100 or may be a separate camera that isconnected electronically or can pass its image to the handheld device100. FIG. 3 also includes a schematic feature of the upper eyelash 306,the lower eyelash 308, a diagram center line 314, and illuminationreference lines 316.

The addition of a fundus imaging system 300 to the handheld device 100opens the possibility to couple analysis of an image of the retina 304with the results of vision testing. If areas of the vision field aredetermined to show distortion, reduced clarity, limited acuity, or othereffects, these can be compared to areas of the retina corresponding tothat area of the vision field. In this way, automated or professionalanalysis of the fundus image can include additional attention in areaswhere the vision field showed limited or poor performance. And, in areverse fashion, areas of the fundus image that show signs of eyedisease can be given additional attention in the automated visiontesting. The combination of both vision testing and fundus imageanalysis is novel and is a key aspect of some possible embodiments ofthis invention.

Although the description above contains many specificities, these shouldnot be construed as limiting the scope of the invention, but as merelyproviding illustrations of some of the presently preferred embodimentsof this invention. Thus the scope of the present invention should bedetermined by the appended claims and their legal equivalents, ratherthan by the examples given. Those skilled in the art to which thisapplication relates will appreciate that other and further additions,deletions, substitutions and modifications may be made to the describedembodiments.

What is claimed is:
 1. A calibration system for use with a vision testerhaving a display, comprising: a calibration stand configured to holdsaid vision tester; and a reflective surface coupled to said calibrationstand and oriented substantially parallel to said display, said standconfigured to hold said display at a fixed distance from said reflectivesurface.
 2. The calibration system as recited in claim 1 wherein saidreflective surface is configured to reflect images displayed on saiddisplay to a camera of said vision tester to allow said vision tester toemploy said reflected images to calibrate and verify functionality ofsaid vision tester.
 3. The calibration system as recited in claim 2wherein said images include varying colors, shapes and brightness. 4.The calibration system as recited in claim 2 wherein said images includecalibration images.
 5. The calibration system as recited in claim 2wherein said images move.
 6. The calibration system as recited in claim1 wherein said vision tester includes calendar functions configured toremind a user to employ said calibration system to calibrate and verifyfunctionality of said vision tester.
 7. The calibration system asrecited in claim 1 further comprising at least one security featureconfigured to protect information and privacy.
 8. The calibration systemas recited in claim 1 wherein said vision tester includes damageassessment functions configured to prompt a user to employ saidcalibration system to calibrate and verify functionality of said visiontester.
 9. The calibration system as recited in claim 1 furthercomprising an auxiliary camera configured to capture an image.
 10. Thecalibration system as recited in claim 9 wherein said auxiliary camerais configured to communicate with said vision tester.
 11. Thecalibration system as recited in claim 9 wherein said auxiliary camerais configured to communicate with an external device.
 12. A calibrationsystem for use with a vision tester having a display, comprising: areflective surface oriented and configured to reflect images displayedon said display; and a camera associated with said vision tester andconfigured to allow said vision tester to employ said reflected imagesto calibrate and verify functionality of said vision tester.